There's a significant price differentiation between living in Manhattan and in other boroughs. One really can't lump them all together.
I have friends that pay $6-700/mo for rooms in reasonable apartments in convenient locations in Brooklyn (e.g. off the Lorimer L stop, less than 10 mins from Union Square). Rents have also significantly gone down in NYC in the past two years. I had mine decreased by 12% last year and it hasn't gone up since.
10 minutes to Lorimer? It's 20 minutes minimum just to Bedford. And that's when the trains are running frequently and efficiently. There have been plenty of times when the L train's taken over an hour to get just to Bedford.
And that doesn't include the walk from the station to your home, which could easily be 10 or more minutes away from the L stop.
I have friends that pay $6-700/mo for rooms in reasonable apartments in convenient locations in Brooklyn (e.g. off the Lorimer L stop, less than 10 mins from Union Square). Rents have also significantly gone down in NYC in the past two years. I had mine decreased by 12% last year and it hasn't gone up since.